Note: Descriptions are shown in the official language in which they were submitted.
CA 02836379 2013-11-15
WO 2012/154656
PCT/US2012/036751
DEVICE WITH ECHOGENIC COATING
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority to provisional application Serial No.
61/483,089, filed May 6, 2011.
FIELD OF THE INVENTION
[0001 j The present invention relates to devices with enhanced
echogenicity for better visualization in ultrasound imaging and methods for
enhancing echogenicity of a device.
BACKGROUND OF THE INVENTION
[00021 Ultrasound technology has advantages over other imaging
modalities. Along with the health advantage of reducing or eliminating
exposure to x-rays (fluoroscopy), the equipment needed is small enough to
move and it has advantages in diagnosing sub-surface tissue morphology.
Furthermore, ultrasound transducers can be made small enough to place inside
the body where they can provide better resolution than is currently available
with magnetic resonance imaging and x-ray computed tomography. Further,
interventional tool or device enhancements which increase their echogenicity
to
accommodate ultrasound enable clinicians to quickly and properly treat
patients, saving time and money.
[00031 Many interventional tools and instruments are designed with
polished surfaces that render the instruments virtually invisible on
ultrasound.
Interventional tools and instruments are herein referred to as "device(s)÷.
The
present invention relates to an enhancement to increase echogenicity of
interventional devices. Interventional devices include, but are not limited
to,
septal puncture needles as well as implantable devices, such as, but not
limited
to, stents, filters, stent graphs, and/or heart valves.
[0004] Ultrasound image device enhancement or "echogenicity has
been studied for many years. When sound waves contact a smooth surface,
the angle of incidence and reflection are the same. If the object is located
at a
steep angle most or all the sound waves bounce away from a transmitting/
receiver source. With such steep angles, even highly reflective devices can be
1
CA 02836379 2013-11-15
WO 2012/154656
PCT/US2012/036751
invisible by ultrasound if scattering does not direct sound back to a source
transducer, Conversely, if an object is perpendicular, the sound waves
reflecting directly back may cause a "white our effect and prevent the
operator
from seeing around the object. This affect is referred to as specular
reflection.
[0005] Medical device manufacturers have tried a variety of techniques
to improve visibility of devices to ultrasound, Examples include roughening
the
surface of the device, entrapping gas, adhering particles to substrate
surfaces,
creating indentations or holes in the substrates and using dissimilar
materials,
SUMMARY OF THE INVENTION
[0006] An aspect of the present invention relates to an echogenically
enhanced interventional tool or device. The interventional tool or device to
be
imaged ultrasonically has an outer surface with a fused polymer particle
coating
affixed to at least a portion of the outer surface of the tool or device.
[0007] Another aspect of the present invention relates to a method for
enhancing echogenicity of an interventional tool or device through the
attachment of biological elements to the surface of the interventional tool or
device. In this embodiment, the interventional tool or device may have an
initially smooth surface onto which biological elements attach; thereby
increasing the surface roughness and echogenicity.
[0008] Another aspect of the present invention relates to a method for
enhancing echogenicity of an interventional tool or device. In this method, a
fused polymer particle coating is affixed to at least a portion of the
interventional tool or device.
BRIEF DESCRIPTION OF THE FIGURES
[0009] Figure 1 shows an interventional tool or device.
[0010] Figure 2 shows the same interventional tool or device of Figure 1
coated with fused polymer particles.
[0011] Figure 3 is a bar graph showing results of a comparison of the dB
increase above control of a device of the present invention with a fused
polymer particle coating as depicted in Figure 2, a spray coating of a
solvated
polymer, and another commercially available coated device.
[0012f Figure 4 is a plot of the reflected energy at various angles, which
reflects increased echogenic response.
2
CA 02836379 2013-11-15
WO 2012/154656
PCT/US2012/036751
DETAILED DESCRIPTION OF THE INVENTION
[0013] The echogenically enhanced device of the present invention
comprises a device to be imaged ultrasonically having an outer surface at
least
a portion of which is affixed with a fused polymer particle coating.
[0014] Examples of interventional tools or devices which can be
enhanced visually in ultrasound imaging in accordance with the present
invention include, but are not limited to, medical devices such as permanent
implantable or temporary indwelling devices, such as catheters, guide wires,
stents and other accessories and tools, surgical instruments, and needles,
such
as septal puncture needles. However, as will be understood by the skilled
artisan upon reading this disclosure, the techniques described herein for
visually enhancing a device via ultrasound imaging are adaptable to many
different fields and devices.
[0015] Echogenicity of this device is enhanced in accordance with the
present invention by affixing to at least a portion of the outer surface of
the
device a fused polymer particle coating.
[0016] In one embodiment, the fused polymer particles of the coating are
at least partially interconnected. Depending on the degree of echogenic
enhancement desired, lower concentrations of polymer particles may be
employed so that some particles while adhered to the device may not be fused
to an adjacent polymer particle or particles.
[0017] In one embodiment, the fused polymer particle coating provides
an irregular surface topography on the outer surface of the tool or device.
This
irregular surface topography produces a unique, visible signature on the
device
when viewed with ultrasound. Depending on the end device application, an
alternate desirable embodiment may include areas of fused polymer particles
wherein the topography is flat and/or even concave.
[0018] In one embodiment, the fused polymer particle coating has a
surface roughness greater than 0.5% of a selected ultrasonic imaging
wavelength. For example, for ultrasonic imaging at 7.5 MHz the wavelength is
200 pm. Thus at this ultrasonic wavelength, in this embodiment the fused
polymer particle coating has a surface roughness of greater than 1 pm (0.5% of
200 pm).
(00191 One embodiment of the fused polymer particle coating may
comprise fused fluoropoiymer particles, fused silicone particles, fused
polyolefin particles, and the like. Examples of fused fluoropolymer particles
for
3
CA 02836379 2013-11-15
WO 2012/154656
PCT/US2012/036751
use in the coatings of the present invention include, but are not limited to,
fluorinated ethylene propylene (FEP) and fluorinated ethylene propylene
perfluora alkyl vinyl ether, or polytetrafluoroethylene-co-vinyl acetate. Of
particular interest is a particle of PTFE (which can be screened to an exact
and
certain size). The PTFE particles are then bonded to the medical device or
implant with FEP or ethylene fluoroethylene propylene (EFEP). It is possible
to
achieve the same results by using differing melt flow indices of the same
polymer.
[0020] In one embodiment, the fused polymer particle coating has a melt
temperature of less than 300 C. In another embodiment, the fused polymer
particle coating has a melt temperature of less than 200 C In yet another
embodiment, the fused polymer particle coating has a melt temperature of less
than 170 C. In another embodiment, the fused polymer particle coating has a
melt temperature of less than 140 C. In other embodiments, the fused polymer
particle has an amorphous state with no defined melt temperature.
[00211 An important aspect of the present invention is the need to select
polymer particles that will produce a fused particle coating without adversely
affecting the nature and function of the device to be imaged.
[0022] In another embodiment of the present invention, the echogenicity
of an interventional tool or device is enhanced through the attachment of
biological elements to the surface of an interventional tool or device, In
this
embodiment, the interventional tool or device may have an initially smooth
surface onto which biological elements attach. Biological elements include
blood cell, fibrin, platelets, and the like. To encourage the attachment of
biological elements, the interventional tool or device may comprise a surface
coating such as fibrin or positive charges by means such as, but not limited
to,
a thin polyethylene irnine coating,
[0023] Enhanced echogenicity of a device according to an aspect of the
present invention was demonstrated experimentally. Results are depicted in
Figure 3 which shows a comparison of the dB increase above control of a
device according to an aspect of the present invention and an Angiotech
coated device.
[0024] The following non-limiting examples are provided to further
illustrate the present invention.
4
CA 02836379 2013-11-15
WO 2012/154656
PCT/US2012/036751
EXAMPLES
Example 1: Materials
[00251A stainless steel needle with the dimensions of 0.040" diameter
and approximately 4.8" long was used as the test article for echogenic
enhancement. An unmodified needle was used as control to compare the
results of the modification. Echogenicity of a stainless steel needle coated
with
a fused polymer particle coating was also compared to an Anglotech coated
needle (Angistech Pharmaceuticals, Inc., 1618 Station Street, Vancouver, BC
Canada V6A 1B6). In addition, a second embodiment was prepared by
dissolving a thermoplastic copolymer of TFE and PMVE in solution as
described in US Patent 7,049,380. This solution was sprayed at a rate of 2
rnl/mmn. using a sprayer (Air Atom, Spray Systems Co.) set to 28.2 psig air
pressure to form a fine mist. A smooth needle was then slowly rotated and
passed back and forth through this spray mist for a total of three passes. The
solvent was air dried. The topography of this spray coated device was
increased relative to the base, smooth device surface. The echogenic
response of the coated needle is plotted in Figures 3 and 4, which reflect the
increased echogenic response of the coated needle.
Example 2: Methods
[0026] Three different methods were used to evaluate and compare the
treated samples.
[0027] All samples were subjected to an acoustic wave imaging system.
The testing apparatus consisted of a 7.5 MHz transmitting/receiving transducer
mounted onto a flat bar with a sample holder placed approximately 2.5 cm at
the transducer's focal length. The 7.5 MHz transducer produced a wave length
(A) of 200 microns. At 2.5 cm the width of the signal was approximately 1 mm.
The needle sample was placed into a holder that is perpendicular to the axis
of
the emitting transducer. This is 0 degrees. The sample holder is removable for
ease of changing out the sample. The holder is magnetically held in a
rotatable
device for measuring the angle of the sample relative to the transmitting and
receiving transducer. The sample and transducer were submerged into a room
temperature water tank. Before collecting the data, every sample was aligned
with the transducer. This was accomplished by increasing the attenuation
setting on the pulser/receiver controller (approximately 40 dB) to prevent
saturation of the received signal. The operator then visually monitored the
CA 02836379 2013-11-15
WO 2012/154656
PCT/US2012/036751
wave signal while manually rotating the goniometer and dialing the fine
adjustment knobs on the transducer to achieve a maximum return signal. The
attenuation was adjusted to a reference point of approximately 1 volt. The
attenuation setting and the goniometer indication were recorded. The
goniometer was rotated 10 degrees from the recorded indication. Since the
signal typically decreases off of perpendicular (specular reading) the
attenuation was reduced. The reduced level allowed a strong enough signal
during collection, without saturation of the receiver. The sample was rotated
through the entire angular rotation to ensure that the signal did not saturate
or
significantly move away from or closer to the transducer moving the signal out
of the data collection window, Significant time shift was an indication that
the
transducer was not aligned with the center or pivot of the sample, Once the
set-up was completed, the goniometer was moved to the 10 degree mark and
the collection of points was taken to 50 degrees at 2 degree increments
Equipment connected to the transducer and test fixture measured reflection.
The software, Lab View and hardware were used for data collection and later
analysis.
[0028] A second evaluation of samples was performed in a silicone
phantom submersible in a blood substitute from ATS laboratories to increase
attenuation and create a more realistic image environment. Using a 6.5 mElz
transducer ultrasound system, the samples were inserted into the phantom. A
still image was captured for each sample, These images were visually
compared to control images and inspected for consistency with the transducer
2D data. The data was collected at three different times. Between collections
two and three, the transducer was rebuilt. Thus, while the absolute dB scale
of
plots is not the same, the relative deltas are of importance.
[0029] The third evaluation was a surface analysis using an optical
comparator. All raw data was further processed by the machine software to
better evaluate the samples. The macroscopic tilt and cylindrical curvature
were removed. A Gaussian filter (Fourier) was selected to filter frequencies
below 20-1mm. Incomplete interior points were restored with a maximum of 3
or 5 pixels. All samples were masked at the edges to remove large data drop
out sections and anomalies associated with the filtering. 2D samples were
processed first followed by 3D samples.
[0030] Total roughness height, Rt or PV, which is the maximum peak to
valley height of the surface profile within the assessment length, was used to
characterize surface roughness.
6
CA 02836379 2013-11-15
WO 2012/154656
PCT/US2012/036751
10031] A comparison of the dB increase above control of a device of the
fused particle embodiment, the SCP coated embodiment, and an Angiotech
coated device is depicted in Figure 3.
7
